Not Applicable.
Not Applicable.
1. Field of the Invention
The present invention relates to energy storage devices. More particularly, the present invention is directed to energy storage devices taking the form of locomotion machines using springs.
2. Description of the Background
Pogo sticks have long been enjoyed by children, but the play experience has been limited to bouncing in place, trying to locomote forward, and negotiating small obstacles. Conventional pogo sticks generally employ inefficient steel compression springs. These pogo sticks provide only a few inches of ground clearance and require the rider to exert substantial effort on every bounce to keep hopping.
Steel compression springs typically have a specific energy limited to 1200 inch-pounds/pound of mass. A steel spring of one (1) pound mass may store 1200 inch-pounds of elastic energy, and theoretically could lift its own weight. 1200 inches vertically and could lift a 150-pound load, the weight of an average person, a total height of 8 inches above the bottom most point when the steel spring is compressed. Accordingly, a two (2) pound spring would be necessary to exhibit a more desirable pogo stick lift of sixteen (16) inches, which would result in an eight (8) inch rise above the ground.
A second disadvantage of the steel compression spring used in conventional pogo sticks is its propensity to buckle laterally. That is, if the spring is held at its two ends and compressed, at some level of compression the middle of the spring will shift sideways and the spring no longer operates in its normal symmetric mode. Coil springs with an aspect ratio of greater than about 6:1 ratio exhibit buckling when substantially compressed, wherein the aspect ratio is defined as the ratio of free length to nominal coil diameter. A typical pogo stick spring has an aspect ratio around 8:1 or higher, so buckling is inevitable. This spring must be guided laterally which can cause significant sliding friction between the spring and the pogo stick plunger.
Yet another disadvantage of the steel compression springs used in conventional pogo sticks is that they have linear force/deflection characteristics. This results in the peak force at maximum compression being nearly twice the average force. The average force is defined by the total work on the spring during compression divided by the stroke length.
Accordingly, there is a need for a pogo stick having an efficient energy storage device resulting in the pogo stick providing a large amount of ground clearance while requiring a minimal effort to keep hopping.
There is a further need for a pogo stick having a configuration that precludes the sliding friction inherent in the conventional pogo sticks having steel coil springs.
The present invention provides a locomotion device using a leaf spring as the energy storage device.
The present invention further provides a leaf spring in the form of a high-performance composite spring material such as fiberglass/epoxy or graphite/epoxy that can store at least two times more energy than a conventional steel coil spring having the same weight.
The present invention further provides a leaf spring energy storage device that bends and is pivoted at the top and bottom ends of the pogo stick such that energy losses from sliding friction associated with lateral buckling are substantially eliminated.
Further, the force/deflection characteristics of the present invention may be tailored for the best performance in terms of energy storage and operator comfort such that one embodiment of the present invention with an adult rider exhibits hopping heights of thirty (30) inches or more as measured from the base of the device to the ground, compared to approximately five (5) inches for commercially available pogo sticks.
The present invention further provides a pogo stick that uses rollers to guide the plunger that further improve the overall efficiency and performance of the pogo stick.
The present invention further provides a leaf spring that provides nearly constant force, allowing nearly twice the energy storage of a linear spring having the same plunger stroke and maximum force. In some such embodiments of the present invention, the spring force increases by only 20% from its initial to its fully compressed value thus, giving nearly constant force over the full range.
Other details, objects and advantages of the present invention will become more apparent with the following description of the present invention.